1. Field of the Invention
The present invention relates to an electric actuator and in particular to an electric actuator with a manual adjustment mechanism.
2. Description of Related Art
The electric actuator has been commonly used as an actuating device to drive the furniture, for example, to open or close the door, or to adjust the inclination angle of the hospital bed. The electric actuator generally includes an external tube in which an actuating shaft is disposed. The actuating shaft is hollow and a screw rod is disposed therein. One end of the actuating shaft is engaged with the tread of the screw rod. A motor disposed in the electric actuator connects and axially rotates the screw rod. As the screws rod axially rotates, the actuating shaft axis is driven to move axially. When the electric actuator is used for adjustment of the hospital bed, one end of the external tube is affixed to the bed frame and the actuating shaft is connected to the bed surface. In order to adjust the inclination angle of the bed surface more precisely, a manual adjustment mechanism can be disposed on the electric actuator for the operator's fine tune.
The conventional manual adjustment mechanism generally uses a sleeve sleeved around the actuating shaft to drive the actuating shaft to rotate with respect to the screw rod and move the actuating shaft. Besides, a locking mechanism is disposed in the manual adjustment mechanism such that when the move rotates the screw rod, the locking mechanism locks the actuating shaft which can not rotate axially. Because a considerable force is applied to the electric actuator in operation and the locking mechanism includes many small parts whose strengths are less than those of other parts of the electric actuator, the force applied tends to make errors to deflect the electric actuator.
In view of this, the inventor pays special attention to research with the application of related theory and tries to overcome the above disadvantages regarding the above related art, which becomes the goal of the inventor's improvement.